Modern packaging machines typically comprise an upstream pouch making section where pouches are made and a downstream pouch filling section where pouches are opened, filled with material and then typically sealed or otherwise closed. The pouch filling section includes an endless carrier which typically comprises an endless chain that picks the pouches from the pouch making section, advances the pouches through various stations in order to fill the pouch with material and then drops off the filled pouch. Although continuous motion type packaging machines driven by a continuous drive mechanism have been provided by the prior art, intermittent type packaging machines have been more common. Intermittent type packaging machines advance the pouch intermittently or step-by-step in which the pouch forming, filling and sealing operations take place when the pouches dwell between successive steps. The success and durability of intermittent type packaging machines is evidenced by the large number of older intermittent packaging machines still in use today (some machines dating back over 30 or 40 years).
In the past, the pouches were typically constructed from relatively rigid materials such as heavy paper or foil. The material was sufficiently rigid such that the pouch when opened maintained an open shape when only held at one end. As such, many of the endless carriers of prior packaging machines typically only hold the pouch with one clamp such as those disclosed for example in U.S. Pat. Nos. 4,580,473, 2,745,583 and 2,649,674. With these prior machines, changing the size or width of the pouch does not require modifications of the endless carrier.
However, with advances in material technology, more modern type pouches are typically made from more flexible materials such as plastic. The pouches are not capable or not as capable of maintaining an open shape for filling and sealing operations. These modern pouches require the need for leading and trailing clamps for holding pouches therebetween, details of examples can be had to U.S. Pat. Nos. 3,568,402, 3,430,414, 4,423,583, and 3,269,524. The leading clamp holds the leading edge of the pouch while the trailing clamp holds the trailing edge of the pouch. To open the pouch, one of the clamps is movable relative to the endless chain and toward the other clamp to provide enough slack such that the bag may be opened. A common way of opening the pouch (for both the single clamp and leading/trailing clamp endless carriers) has been to use a vacuum mechanism which pulls the sides of the pouch apart at the filling station. Thus, two operations are performed at the filling station to first open the pouch and then fill the pouch with the desired material.
While the utilization of leading and trailing clamps has reliably supported and opened the pouches, packaging machines that use leading and trailing clamps have not been able to accommodate different sizes of pouches. A packaging machine is typically dedicated to only one width size of pouch dictated by the distance between leading and trailing clamps. Therefore a complete retooling of the packaging machine is necessary to accommodate a new width size of pouch. Therefore, product packagers have not been readily or easily able to change the size of the pouch. This also requires product packagers to have several differently configured machines for different package sizes for their product lines.
Another concern of product packagers is maintaining a high rate of production which therefore requires an index cycle rate which minimizes the dwell time during each successive step and the time for advancing the pouches between steps. As a practical matter, the dwell time must be long enough to provide sufficient time to perform each of the steps at each of the stations. In prior machines, the dwell time is often limited by the rate at which pouches are filled at the filling station. In any event, it is desirable to both minimize the necessary dwell time and maintain the dwell time as close as possible to the required dwell time for performing the various steps at the stations during each dwell.